The present invention relates to the chemical mechanical planarization of semiconductor wafers using a fixed abrasive substrate. More particularly, the present invention relates to an improved system and method for chemical mechanical planarization in which the manufacturing of the fixed abrasive substrate occurs in situ, being incorporated into the same process path as the chemical mechanical planarization process.
Semiconductor wafers are commonly constructed in layers, where a portion of a circuit is created on a first level and conductive vias are made to connect up to the next level of the circuit. After each layer of the circuit is etched on the wafer, an oxide layer is put down allowing the vias to pass through but covering the rest of the previous circuit level. Each layer of the circuit can create or add unevenness to the wafer that must be smoothed out before generating the next circuit layer.
Chemical mechanical planarization (CMP) techniques are used to smooth or planarize the raw wafer and each layer of material added thereafter. Available CMP systems, commonly called wafer polishers, often use a rotating wafer holder that brings the wafer into contact with a polishing pad rotating in the plane of the wafer surface to be planarized. A planarization liquid or CMP slurry is applied to the polishing pad to facilitate the removal of material from the surface of the wafer.
The polishing pad may utilize a loose or a fixed abrasive. In the case of a loose abrasive, the polishing pad is generally made from a nonabrasive material, and the planarization liquid is generally a CMP slurry containing abrasive particles and chemicals that remove material from the surface of the wafer. In the case of a fixed abrasive, the polishing pad is generally made from a mixture of abrasive particles in a binding agent affixed to a backing or substrate, and the planarization liquid generally does not contain abrasive particles.
The fixed-abrasive substrate can be produced in any form that can be used in a CMP polishing process. A variety of forms are commonly used, including a continuous roll, a closed loop, annular disks, and round disks. With respect to the CMP process, the fixed-abrasive substrates are generally considered consumable products. Fixed-abrasive substrates are usually purchased from a third party supplier and are very expensive. One example of such a fixed-abrasive substrate is produced by 3M and distributed by Rodel.
In one aspect, the present invention provides methods and apparatus for combining the manufacturing of a fixed-abrasive substrate and the chemical mechanical planarization of semiconductor wafers using a single process path.
In another aspect, the present invention provides methods and apparatus which allow both continuous fixed-abrasive substrate manufacturing and continuous wafer polishing using a single process path.
In another aspect, the present invention provides methods and apparatus for combined manufacturing of a fixed-abrasive substrate and wafer polishing where the components of the fixed-abrasive substrate can be reclaimed and recycled for further use in a fixed-abrasive substrate manufacturing process.